Effect of Calcium Supply on Photosynthesis and Ultrastructure of Cells of Kandelia obovata(S.L.)Yong Under Cadmium Stress

This paper studies the effect of various Ca concentrations on Cd-stressed mangrove species(Kandelia obovata(S.L.)Yong).9cross-deals were designed completely randomly using Hoagland nutrient solution culture experiment with Cd concentration of 0,0.5,5.0mg/L and Ca concentration of 0,400,800mg/L.Photosynthetic index,chlorophyll content,and leaf tissue anatomy of chloroplast ultrastructure of mangrove plants were observed under these experimental conditions.Results showed that Cd stress significantly reduced the net photosynthetic rate,stomatal conductance,intercellular carbon dioxide concentration and transpiration rate of K.obovata.The chlorophyll content decreased under Cd stress,indicating that Cd ion had some damaging effects on K.obovata photosynthetic system.Addition of exogenous Ca ion to K.obovata significantly increased the leaf photosynthetic indexes and the chlorophyll content indicating that Ca had a strong promoting effect on the photosynthesis of K.obovata.Therefore,Ca could,to some extent,alleviate the "dry formation" of leaf anatomy of K.obovataunder the heavy metal stress,but differences in the anatomy of the change was not significant.Our data also showed that Ca ions have some protection and relief on Cd-induced cell structure damage.Our results revealed the effect of Ca on heavy metal resistance of mangrove plants in photosynthesis and ultrastructural characterization,and discovered the mechanisms of heavy metal tolerance and key control factors.Our study provides a new theoretical basis for dealing with heavy metal pollution in mangrove ecosystems and a new way to restore polluted mangroves.